There are some exciting developments in the online map space these days. WikiMapia is a wiki approach to Google Maps that let’s you add notes and tags to maps all over. MapCruncher is a program that lets you draw maps on top of other maps (or something like that). I haven’t been able to try out the latter yet due to some of the requirements, but I’m hoping it’ll come together soon as it sounds very promising.
UPDATE: I finally got MapCruncher to work. It requires Windows XP and the .NET 2.0 runtime, which is not as obvious as the Web site makes it sound. Also, rendering the map (overlaying the north-side map of the Chicago El on Virtual Earth) took about 18 minutes, not the 5-10 the site suggests.